Optoelectronic components of the kind mentioned above are previously known. A light emitting diode (LED) and a photodetector, for example, are arranged in a housing close to the end of a light guide. The LED may then, for example, be arranged in the extension of the longitudinal direction of the light guide. A partially transmitting mirror is arranged between the LED and the end of the light guide, and the mirror deflects light entering through the light guide in a direction towards the photodetector. By a partially transmitting mirror is meant here a member which partially transmits and partially reflects incident light.
It is known, per se, to arrange an LED of the above-mentioned kind such that it is to a certain extent adjustable in relation to the housing, for example by providing a certain play between the LED and the housing. During assembly of the component, the light guide is first mounted in the housing, whereupon the LED is placed in the housing and connected to a current source. The intensity of the light flowing out from the remote end of the light guide is measured, and the orientation of the LED is adjusted so as to obtain a maximum value of this intensity. In this position, the LED is mechanically locked to the housing, for example with the aid of quick curing plastic, whereupon, if desired, any gaps between the LED and the housing may be filled with plastic to obtain good mechanical stability of the components.
The above-mentioned method of adjusment, however, is less suitable for a photodetector. Generally, the light guide is not exactly centered in the housing. Further, its longitudinal direction normally deviates from the ideal direction. The angle of the partially transmitting mirror generally deviates somewhat from the theoretically correct one. Likewise, the light-receiving semiconductor element of the photodetector is generally not exactly accurately located in a plane perpendicular to the optical axis of the detector. For these reasons, the radiation which is caused to become incident upon the semiconductor element of the photodetector will generally not be centered in relation to the semiconductor element. In known components of the kind described here used up to the present, this fact has necessitated the use of a relatively large area of the semiconductor element of the photodetector, the reason for this being to ensure that a sufficiently large part of the radiation which is incident upon the detector really hits the detector despite the above-mentioned unavoidable error sources. Since the performance of a large-area photodetector is inferior to that of a small-area detector, prior art components have possessed less good operating properties than what would have been theoretically possible.
From EP-A10 250 331, it is previously known to arrange a light-emitting member and a light-detecting member in the same housing for bidirectional optical signal transmission via one and the same optical fibre. In this device, both members lack possibilities of adjustment, and therefore especially the photodetector has the disadvantages mentioned in the preceding paragraph.
From FR-A1 2 586 305 a component of the same kind is previously known, in which the end surface of the optical fibre is obliquely bevelled for optical coupling to one of the members by reflection at the end surface and to the other member by refraction at the end surface. The desired bevelling of the end surface of the fibre is difficult to achieve from the point of view of manufacturing with the desired accuracy. Further, the light reflected by the end surface of the fibre is diffusely scattered during its passage through the envelope surface of the fibre, which considerably deteriorates the optical coupling between the fibre and that of the two optoelectronic members which utilizes the light reflected at the end surface. This diffuse scattering also causes the adjustment to become more complicated and--in the event the member in question is a photodetector--necessitates the provision of a relatively large area for the member, which deteriorates the operating properties of the member.
IBM Technical Disclosure Bulletin Vol. 33, No. 1A, June 1990, pages 456/457, shows a component with one single optoelectronic member, a laser diode, which emits light via a lens. To be able to align the laser diode in relation to the lens, double spherical bearings are arranged, which permits alignment in five degrees of freedom. The simultaneous alignment of the two spherical bearings becomes complicated.